Planned myopic astigmatism as a substitute for accommodation in pseudophakia
Abstract
Patients with an implanted intraocular lens can be made nearly spectacle independent by increasing the depth of focus of the uncorrected implanted eye. In simple myopic astigmatism the visual acuity can be above 20/50 from far to near because the size of the blurred retinal image changes less than its shape as an object approaches the eye. For simple myopic astigmatism the change in corneal power must be included in the calculation of intraocular lens power. The change in corneal power induced by surgery is a spherocylinder with no spherical equivalent. The postoperative shape of the cornea can be predicted and intraocular lens power is calculated to make the flatter meridian emmetropic. The stronger meridian of the cornea is then myopic. In a series of 40 successive cases, the refractions and the measured depth of focus illustrate the application of these principles and the advantage of myopic astigmatism for the pseudophakic patient.
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Cited by (80)
Citation network analysis of the various types of multifocal intraocular lenses
2021, Archivos de la Sociedad Espanola de OftalmologiaLa implantación de lentes intraoculares (LIO) multifocales se ha incrementado en los últimos años, permitiendo a los pacientes una calidad de visión en todas las distancias, una independencia de la gafa y, en consecuencia, un aumento de la calidad de vida. El objetivo de este estudio es analizar las relaciones entre publicaciones y autores mediante las redes de citación, así como identificar las distintas áreas de investigación y determinar la publicación más citada.
La búsqueda de publicaciones se realizó mediante la base de datos Web of Science, empleando los términos «Multifocal intraocular lens», «Bifocal intraocular lens», «Trifocal intraocular lens», «Diffractive intraocular lens», «Refractive intraocular lens», «Accommodative intraocular lens» y «Extended depth of focus intraocular lens», en un intervalo de tiempo entre 1989 y agosto del 2020. Para el análisis de las publicaciones se empleó el software Citation Network Explorer.
Se encontraron 1.293 publicaciones con 11.730 citaciones generadas en la red, siendo el año 2019 el de mayor número de publicaciones. La publicación más citada es «European multicenter study of the AcrySof ReSTOR apodized diffractive intraocular lens», de Kohnen et al., publicada en el año 2006. Mediante la función Clustering se encontraron cuatro grupos sobre distintas áreas de investigación en este campo, tales como: calidad visual, diseños de LIO, aberraciones oculares o curvas de desenfoque.
La red de citaciones muestra un análisis exhaustivo y objetivo de los principales trabajos sobre los distintos diseños y clases de LIO multifocales.
The implantation of multifocal intraocular lens (IOL) has increased in recent years, allowing patients to achieve good quality vision at all distances, independence from use of glasses, and consequently, an increase in quality of life. The main purpose of this study was to analyse the links between publications and authors via citation networks, as well to as identify the different research areas and determine the most cited publications.
The publication search was performed through the Web of Science database, using the terms «Multifocal intraocular lens», «Bifocal intraocular lens», «Trifocal intraocular lens», «Diffractive intraocular lens», «Refractive intraocular lens», «Accommodative intraocular lens» and «Extended depth of focus intraocular lens», for a time interval from 1989 to August 2020. The software used to analyse the publications was the Citation Network Explorer.
A total of 1293 publications were found, with 11730 citations generated in the network, and 2019 had the highest number of publications of any year. The most cited publication was «European multicenter study of the AcrySof ReSTOR apodized diffractive intraocular lens» by Kohnen et al., published in 2006. Four groups about different research areas in this field were found using the Clustering functionality: visual quality, IOL designs, ocular aberrations, or defocus curves.
The citation network offers an objective and comprehensive analysis of the main articles on the different designs and classes of multifocal IOL.
Pupil influence on the quality of vision in rotationally asymmetric multifocal IOLs with surface-embedded near segment
2017, Journal of Cataract and Refractive SurgeryTo evaluate the influences of preoperative pupil parameters on the visual outcomes of the SBL-3, a rotationally asymmetric multifocal intraocular lens (IOL) with a surface-embedded near segment.
Cathedral Eye Clinic, Belfast, Northern Ireland, United Kingdom.
Retrospective comparative case series.
Postoperatively, patients divided into 4 groups according to their pupil size as follows: Group A: 2.50 to 2.99 mm, Group B: 3.00 to 3.50 mm, Group C: 3.51 to 4.00 mm, and Group D: 4.01 to 4.50 mm. The uncorrected distance (UDVA), intermediate (UIVA), and near (UNVA) visual acuities, IOL centration and tilt, and quality of vision (QoV) questionnaires were compared between the 4 groups for 18 months postoperatively.
The study comprised 90 patients (180 eyes). The mean preoperative pupil (photopic and mesopic) diameter was 4.3 mm ± 0.3 (SD) and 5.6 ± 1.4 mm, respectively, which decreased to 3.8 ± 0.7 mm and 4.9 ± 1.2 mm, respectively, at 18 months. Eighteen months postoperatively, both photopic and mesopic pupil groups had a statistically significant reduction in size from preoperative levels. No significant differences in UDVA, UIVA, and UNVA were found between the groups (P > .001). Significant differences in the QoV questionnaire day scores and night scores were found between the 4 groups (P < .001).
The rotationally asymmetric multifocal IOL provided excellent optical performance during 18-months follow-up. The preoperative photopic pupil is an important parameter for consideration of this type of IOL because smaller pupils have a significant negative subjective impact on QoV.
The effect of corneal wavefront aberrations on corneal pseudoaccommodation
2012, American Journal of OphthalmologyTo determine the effect on corneal pseudoaccommodation of anterior corneal wavefront aberrations in normal corneas and corneas with prior myopic or hyperopic photorefractive keratectomy (PRK) or laser-assisted in situ keratomileusis (LASIK).
Theoretical study.
In 220 normal eyes, 102 myopic-PRK eyes, and 106 hyperopic-LASIK/PRK eyes, anterior corneal higher-order aberrations (HOAs, third to sixth order, 6- and 4-mm pupils) were computed from the Atlas corneal elevation data using the VOL-CT program. Using the ZernikeTool, corneal optical image quality was evaluated by the polychromatic modulation transfer function with Stiles-Crawford effect. Defocus from −3.0 diopters (D) to +3.0 D was added to corneal HOAs, and depth of focus was defined as the ranges over which the polychromatic modulation transfer function maintains 80% of the peak value (DOF80) and 50% of the peak value (DOF50). The depth of focus values between groups were compared, stepwise multiple regression was used to assess if any Zernike terms significantly contributed to the depth of focus, and correlation analysis was performed to evaluate the correlation between depth of focus and corneal HOAs.
The depth of focus varied widely between corneas, especially in corneas with prior hyperopic-LASIK/PRK. For 6-mm pupil, mean depth of focus values in myopic-PRK and hyperopic-LASIK/PRK corneas were significantly greater than those for normal corneas, and for 4-mm pupil, depth of focus values in hyperopic-LASIK/PRK corneas were greater than those in normal and myopic-PRK corneas. Zernike terms significantly contributing to both DOF80 and DOF50 were fourth- and sixth-order spherical aberration and fourth- and sixth-order astigmatism in normal corneas, third-order vertical coma and fourth-order tetrafoil in myopic-PRK corneas, and third-order vertical coma and fourth-order astigmatism in hyperopic-LASIK/PRK corneas. Depth of focus had weak to moderate positive correlation with HOAs (Pearson correlation coefficient r ranged from 0.300 to 0.583).
These theoretical calculations suggest that certain corneal wavefront aberrations affect corneal pseudoaccommodation. To predict corneal pseudoaccommodation, the most important Zernike term is spherical aberration in normal eyes and coma in eyes with prior laser corneal surgery.
Visual and accommodative outcomes 1 year after implantation of an accommodating intraocular lens based on a new concept
2009, Journal of Cataract and Refractive SurgeryTo evaluate visual outcomes and accommodative gains 1 year after implantation of the NuLens accommodating intraocular lens (IOL).
Department of Refractive Surgery, Vissum Corp., Alicante, Spain.
This study comprised patients with cataract and atrophic macular degeneration. In each patient, the accommodating IOL was implanted in the eye with the worse visual acuity. At the 12-month follow-up visit, visual acuity and accommodation were measured to determine the efficacy of the IOL. Ultrasound biomicroscopy was used to measure accommodative amplitude.
Ten eyes of 10 patients were evaluated. The mean number of lines patients could read increased from 1.0 preoperatively to 3.8 lines 6 months postoperatively, indicating improvement in uncorrected near visual acuity after IOL implantation. The mean change in cross-section measurements of the IOL was 0.06 mm at 1 month; the value peaked at 3 months (0.21 mm), after which it decreased steadily, becoming stable at 9 months (0.09 mm, which is equivalent to 10.00 diopters [D] of accommodation). Corrected near visual acuity improved slightly (0.7 Jaeger lines) at 12 months, with the best reading distance at 10 cm. These results suggest that the near and distance visual acuities were approximately equal and, therefore, the IOL can produce accommodation of 10.00 D.
The accommodation mechanism of the IOL can produce an ocular power variation of 10.00 D. Near visual acuity improved without compromising distance visual acuity.
Effect of Patient Motivation on Near Vision in Pseudophakic Patients
2009, American Journal of OphthalmologyTo investigate the effect of ‘training’ the patients' near vision and motivating them towards a spectacle-independent outcome on near vision performance in pseudophakic patients with standard intraocular lens (IOL).
Prospective randomized, controlled, examiner-masked clinical trial.
Eighty eyes of 40 patients with standard cataract surgery were randomly assigned to a “motivated” or “control” group. In the motivated group, subjects were told that they are taking part in a special protocol to improve their near-reading ability after cataract surgery and were instructed not to use reading glasses for at least three months and received cycloplegic eye drops for 10 days after surgery. Follow-up examinations at three months included best-corrected distance visual acuity (VA), distance-corrected near VA, best-corrected near VA, assessment of the defocus curve, and reading speed, as well as pilocarpine-, cyclopentolate- and nearpoint-induced IOL shift assessed with partial coherence interferometry. Additionally, a questionnaire evaluating patients' postoperative satisfaction, independency of reading glasses, and daily-life performance without glasses was carried out three months and one year postoperatively.
No difference in reading ability and IOL shift between “motivated” and “control” patients could be detected. However, the motivated patients were less dependent on reading glasses and their ability to be able to perform activities of daily life without glasses was significantly better.
There was no improvement of ciliary body function in pseudophakic patients with a special training protocol. However, near vision training made patients more independent of reading glasses.
Using adaptive optics to optimize the spherical aberration of eyes implanted with EDOF and enhanced monofocal intraocular lenses
2024, Journal of Cataract and Refractive Surgery
Presented at the Fourth U.S. Intraocular Lens Symposium, Los Angeles, California, March 27, 1981.